Become a Site Supporter and Never see Ads again!

Author Topic: Stereo Technique with MK41 or other super-cardioid Microphones  (Read 959 times)

0 Members and 1 Guest are viewing this topic.

Offline beenjammin

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 25
Apologies if this has been discussed in another thread. I've searched but haven't come across anything dedicated to stereo techniques with the MK41.

(As an aside, my application is nature recording (bird species), spot-ambience, effects, et al. I typically record ecological soundscapes and have used the MK2 in AB for this application to good effect. I need something with more reach and focus; something mobile which I may run handheld to capture a single bird call/song, street corners, fountains and all other sorts of sounds.)

I know the MK41 does very well in MS with the MK8, but I wonder if there might be suitable stereo configurations with two MK41s.

Does it work in ORTF? NOS? DIN? Something else?

Offline heathen

  • Trade Count: (15)
  • Taperssection All-Star
  • ****
  • Posts: 1221
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #1 on: June 16, 2018, 12:52:48 PM »
You might want to play around with this: http://www.sengpielaudio.com/Visualization-EBS-E.htm

I think a fair number of people on here use DINa with hypers/supers, but I don't remember the measurements for that off the top of my head.
« Last Edit: June 16, 2018, 12:54:25 PM by heathen »
Mics: Core Sound TetraMic | AT4031s | AT AE5100s | AT853s (C/SC) | Line Audio CM3s | CA-14 omnis | Studio Projects CS5
Pre: CA9200
Decks: Zoom F8 | Roland R-05

Offline beenjammin

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 25
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #2 on: June 16, 2018, 01:48:44 PM »
You might want to play around with this: http://www.sengpielaudio.com/Visualization-EBS-E.htm

I think a fair number of people on here use DINa with hypers/supers, but I don't remember the measurements for that off the top of my head.

Thanks, I've been playing around with that applet.

My concern with two MK41s in stereo is over how to treat the null of the super-card's pattern. Our own David Satz posted the following on the REP forum:

"That's crucial for stereo imaging, and it is why a pair of supercardioid microphones must be angled somewhat more narrowly than cardioids would be--to avoid having the null of the left microphone aimed at the direct sound at the right of the stage and vice versa. I'd try 100 degrees as a starting point."

(http://repforums.prosoundweb.com/index.php?topic=7164.0)

I guess this is why the MK41 works well as a run and gun technique in MS: the null of the 41 may be absorbed by the body of the recordist standing behind the microphones.

I'll try to rent a pair of MK41s so that I may play around with angles. I think MS with a MK41/MK8 will suit me best, but want to check out near-coincident configurations first. 

Offline kuba e

  • Site Supporter
  • Trade Count: (1)
  • Taperssection Regular
  • *
  • Posts: 149
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #3 on: June 16, 2018, 04:08:45 PM »
I am sorry, I didn't read all details in discussion you linked. My English is bad, it would take me a long time. I will try to write the basic rules, it could help to understand stereo recording.

The first rule for stereo recording with pair of mics with directional pattern:
- the bigger spacing between mics, the wider stereo recording.  the smaller spacing between mics, the more mono recording.
- the bigger angle between mics, the wider stereo recording.   the smaller angle between mics, the more mono recording.

Spacing is creating stereo image by sound's time difference. Angle is creating stereo image by sound's level difference. Try first bigger angle (e.g. 90 degrees) and small spacing (e.g. 10cm) and the second small angle (e.g. 25 degrees) and bigger spacing (e.g. 35cm). Both variants should give very roughly the same stereo image but with different atmosphere. Compare it.

The second rule:
The microphone is the most sensitive on it's axis. When you need the sound source to be more prominent in comparison to the surroundings, aim the microphones more at the sound source (smaller angle, bigger spacing). Sounds, that are coming out of the mic's axis, are quieter in the recording. Another way to achieve more prominent sound source compared to the surroundings is to get closer to the source (we get a sound level drop of 6 dB per doubling of distance).

You can combine different spacing and angles to get it right for you.

If you have time and energy, the stereo recording theory is very nicely explained in Michael Williams document Stereo Zoom:
http://microphone-data.com/media/filestore/articles/Stereo%20zoom-10.pdf
« Last Edit: June 16, 2018, 05:40:38 PM by kuba e »

Offline DSatz

  • Site Supporter
  • Trade Count: (27)
  • Needs to get out more...
  • *
  • Posts: 2502
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #4 on: June 17, 2018, 09:19:19 AM »
Hi. A couple of thoughts:

- If you're coming from a background of recording with spaced omni microphones, I think you'll find that recording with two coincident or closely-spaced supercardioids gives a fundamentally different overall impression. It's not just a variation by degree from what you're used to. The listener's brain goes into a different mode of listening, because the sense of space and the ability to localize direct sound sources are so different between the two kinds of recording. They're both called "stereo" but they're so different in their effect that I sometimes think there should be different terms for the two approaches. (A/B vs. X/Y comes close; "intensity" vs. "arrival time" differences are involved, but those are ugly terms and anyway, those two principles of operation aren't mutually exclusive in most cases.)

With spaced omnis, if the live environment in which you made your recording was rich and spacious, a similar feeling can be manifest when your recording is played back. It's like bringing that _environment_ into the room where the playback occurs; you may feel as if you are wrapped or "enveloped" by that environment, even with only two channels and two loudspeakers. This encourages a mode of listening in which sensuousness and the color of sound are the main offerings. It invites you to turn off certain critical tendencies, and just take a bath in the sound. If the material being recorded is highly complex, it will be blended and softened and the edges rounded off by this type of recording. That can make it more palatable and atmospheric--sometimes primitive and mystical, even--at the cost of some clarity and specificity. That's where judgment and experience come in, since you may not always want that particular tradeoff.

With directional microphones, particularly coincident supercardioids or crossed figure-8s, you can get a very clear "stereo image"--a representation of the direct sound sources that's consistent over space and time, and that involves your knowing (on some level in your brain) where the direct sound sources were relative to the microphones. This offers much better support if you're consciously trying to grasp the specifics of the content that's being delivered. But esthetically it is a very different type of experience. The emphasis is more on the direct sound sources and where they are and what they're doing; the "atmosphere" is reproduced more quantitatively than qualitatively. Its tradeoff is that it puts more of a cognitive burden on the listener, but with a greater payoff in specific information if the listener chooses to engage that way. But it's not usually as intuitively persuasive as a good spaced-omni recording.

There are crossover and compromise approaches. I like certain aspects of both typological extremes, so I'm very drawn to those crossover approaches in many recording situations. Those include the use of "subcardioid" microphones (in the Schoeps line, that would be the MK 21 and MK 22--the so-called "wide cardioid" and "open cardioid" patterns respectively) with an approach to angling and spacing that's derived from ORTF stereo recording.

- "Reach" is a problematic concept, especially where stereo recording is concerned. A fact of physics that surprises a lot of people is that the highest directivity you can get from a "first-order" microphone (with a single capsule and no special signal processing) only gets you a 2:1 "distance factor" relative to an omni. In other words, if you find that the optimal balance of direct to reverberant sound is obtained when an omni mike is 3 feet from something, then a hypercardioid would give you that same quantitative balance of direct and reverberant sound at 6 feet. No first-order microphone pattern can ever give you that same "3-foot balance" at any greater distance; no microphone can "zoom in on" a more distant sound source and make it seem that close.

For a number of technical reasons, a pair of good supercardioids may well be your best choice when you are forced to record in stereo from all the way into the reverberant sound field. Certainly NOT shotgun microphones, which have highly irregular off-axis response at high frequencies, and no better than supercardioid directivity at low and mid frequencies (i.e. they're useful only when they're close enough to the sound source to pick up enough direct sound on axis so that you don't care about the residue of off-axis sound). But even good supercardioids can't compensate for excessive recording distance. Directional microphones are, if anything, more sensitive to their exact placement than omnis are.

- All that said, there's an interesting variant on omnis that can produce surprisingly good results sometimes, and that is to embed the membranes of each microphone in the surface of a sphere (see attached photo). I wonder whether you've tried this technique with your omnis. (Add-on sphere accessories are available for various microphone diameters.) It's another one of those adaptations or compromises that I spoke of, but this one completely preserves the spaciousness and "envelopment" aspects of spaced-omni recording, while increasing the clarity and directness of the direct sound sources.

Just as food for thought.

--best regards

P.S.: The attached photo shows a Schoeps omni capsule mounted on a Colette active cable and surrounded by a sphere accessory. But such spheres can also slide over the capsule when the capsule is mounted directly on the microphone body (amplifier). The important thing is for the surface of the sphere to be "flush with" the front edge of the capsule. -- This technique works only for omni (pressure) transducers. It would block the rear sound inlet of a pressure-gradient (directional) capsule and mess up both its polar response and its frequency response.

P.P.S: I meant to point out--when you're looking in Williams' charts or on Sengpiel's site or on http://www.hauptmikrofon.de/, be aware that supercardioid and hypercardioid have dictionary definitions which any given microphone probably won't fit exactly. The Schoeps MK 41 isn't exactly a supercardioid; it's like 2/3 supercardioid and 1/3 hypercardioid. Neumann calls their small hybrid a hypercardioid, but it's also in between hyper- and super- (with a slightly different recipe from Schoeps). Similarly, Sennheiser calls theirs a supercardioid, but it has about the same pattern as Neumann's hypercardioid, etc., etc.
« Last Edit: June 17, 2018, 04:02:14 PM by DSatz »
music > microphones > a recorder of some sort

Online goodcooker

  • Trade Count: (24)
  • Needs to get out more...
  • *****
  • Posts: 2530
  • Gender: Male
  • goes to 11
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #5 on: June 17, 2018, 09:25:51 AM »
I'll chime in since I've been running MK41s for a bit and used the hypercard capsule/setting on other mics.

Reconsider this - "I think MS with a MK41/MK8 will suit me best" - when you use a cardioid mid and mix 50/50 you end up with basically a pair of hypercardioid mics. When you use a hyper as the mid and mix the same you end up with a pair of Figure 8. This may or may not be exactly what you are after.

I tend to not use the fixed 90 degree angle DINa pattern (90 degrees/17cm) that was the conventional wisdom for running a stereo pair of hypers. I tend to run a slightly larger spread and a slightly more narrow angle usually between 20-25cm spread and roughly 70 degree angle. I feel that this retains the stereo image but gives more direct to reverberant ratio (more of the source, less of the surroundings) but still has the time arrival differences that make for a pleasing stereo image. I think with microphones like MK41s that have a very realistic off axis sound the spacing is more important than the angle. Of course this is for recording music mostly indoors.

I realize that for recording nature and ambient sounds you may need a different approach and I've always used more open patterns - omnis or subcardioids when doing ambient recordings since I think it sounds more natural.
Schoeps MK41 > nBob > PFA || MBHO KA300 > PFA
Aerco MP2 || RAD MS2
Marantz PMD706 || PMD620

http://www.archive.org/bookmarks/goodcooker

"Are you the Zman?" - fan at Panic 10-08-10 Kansas City

"I don't know who left this perfectly good inflatable wook doll here, but if I'm blowing her up, I'm keeping her." -  hoppedup

Offline beenjammin

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 25
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #6 on: June 17, 2018, 12:04:51 PM »
Thanks very much, DSatz and goodcooker.

DSatz: such an excellent post that nicely expresses what I love about AB, especially with omni. I am aware of the APE spheres and tried them once outside on one of those rare days with very little wind and loved the results. My only issue was how to use them in windy situations. I asked one of the US Schoeps representatives if the APE ball might work inside a W20 R1 wind screen as was advised against this approach.

goodcooker: very interesting approach to the MK41 regarding spacing and angles. Have you ever experienced issues with the microphone's null?

I'm not looking to replace my AB setup. I've been using this for a few years and am very happy with the results. My strategy is hike in somewhere, find a nice spot, hit the record button and clear out for as long as possible. My interest in another stereo technique is motivated by a desire to have something that works handheld while moving about. I'd like to be able to record things from birdsong to trains to interesting air conditioner units. Less ambient, more species/individual focused.

 
 


Online Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 12236
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #8 on: June 25, 2018, 04:43:41 PM »
First a correction on Mid/Side.  I'll make some other comments in a following post.

when you use a cardioid mid and mix 50/50 you end up with basically a pair of hypercardioid mics. When you use a hyper as the mid and mix the same you end up with a pair of Figure 8. This may or may not be exactly what you are after.

The second part of the statement above (which I've bolded) is incorrect.

The only Mid/Side setup able to create a pair of virtual figure-8 patterns is one which uses a figure-8 Mid.. and in that case the Left and Right virtual microphone patterns are always figure-8 shaped regardless of Mid/Side ratio.  In that case, changing the Mid/Side ratio will change the angle between the two virtual 8's but will not change the shape of the virtual pickup patterns.  This behaviour (the virtual polar pattern remaining unchanged regardless of ratio) is unique to Mid/Side done with a figure-8 Mid microphone.  Use of any other polar pattern as Mid microphone means the resulting virtual polar patterns will vary in shape, usually in combination with with the change of virtual microphone angle.  The exception, and corresponding opposite behaviour, is use of an omni Mid microphone.  In that case the virtual pattern varies along with change of ratio, but the virtual microphone angle always remains a constant 180 degrees.

It is correct that a cardioid Mid, used in combination with any Mid/Side ratio which produces a useful stereo pair, will produce a coincident virtual pair with supercardioid-to-hypercardioid shaped sensitivity patterns.  The degree of supercardioid to hypercardioid-ness depends on the Mid/Side ratio used, but the virtual patterns will always somewhere in the supercard to hypercard range, and never actually reach cardioid or figure-8.

It is also correct that use of a supercardioid or hypercardioid Mid will also produce a coincident virtual pair with a supercardioid-to-hypercardioid like sensitivity patterns.  The degree of supercardioid or hypercardioid-ness still depends on the Mid/Side decode ratio used, but the patterns shift more towards the hypercardioid side.  They still never reach virtual figure-of-8 patterns for any stereo Mid/Side ratio, but they get somewhat closer.


volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Online Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 12236
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #9 on: June 25, 2018, 04:53:08 PM »
An additional note on dialing in Mid/Side ratios- Use your ears to determine what is correct, more than your eyes to read the ratio number.  In other words, don't worry what the ratio reads on your Mid/Side control, it's the sound that matters and that ratio display is quite likely lying to you anyway.

Why? 

The Mid/Side control assumes the use of equal sensitivity mics and matched gain between channels.  In addition to the Mid/Side ratio you specify in whatever control you are using, any difference in sensitivity between the Mid and Side microphones and any difference in recording gains between the two channels also affect the Mid/Side ratio.  This is an additive "in addition to" thing (similar to the total gain being the sum of all gain stages- such as preamp gain plus recorder gain), yet the Mid/Side control is blind to any other gain variables which preceded it, meaning that specifying a 50:50 Mid/Side ratio with your Mid/Side control may not actually produce a 50:50 output ratio. This is a commonly overlooked aspect here at TS where folks are quite often using Mid and Side microphones that have differing sensitivities and/or using more gain on the Side channel than the Mid channel to get optimal recorded levels.

If you mix by ear instead of dictating a Mid/Side ratio by number, you automatically accommodate for these issues.  Who cares what ratio number you end up with anyway? Optimizing for best sound is what matters.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Online Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 12236
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #10 on: June 25, 2018, 06:42:35 PM »
Apologies for my OT Mid/Side asides above.  Just wanted to get that stuff that out of the way.

What I mostly wish to contribute to the thread is to echo DSatz's comments on the fundamental difference in overall listening impression between A/B and X/Y microphone techniques - an excellent observation, well stated.  I especially perked up at the mention of "The listener's brain goes into a different mode of listening, because the sense of space and the ability to localize direct sound sources are so different between the two kinds of recording. They're both called "stereo" but they're so different in their effect that I sometimes think there should be different terms for the two approaches."

The bit below may seem OT at first, but I'll explain further down why I think it applies.

I consider near-spaced microphone techniques commonly used around here as attempts at finding optimized middle-ground solutions which effectively bridge the gap between these two very different modes of recording and listening, without moving beyond the constraint of two microphones and two recorded channels.  This can work very well for live music, where we can achieve a respectable balance between immersive ambience, good clarity and sharp imaging using well considered arrangements of two microphones.  Yet I'm rarely completely satisfied with the results given the necessary compromises.  Once I became aware of how well each aspect can be addressed on their own, albeit at the detriment of the other, those compromise solutions all to often no longer satisfy either listening mode for me sufficiently.  Of course there are plenty of exceptions, but the general trend holds.

I want to try and better optimize for both modes of listening at the same time, so I break the listening experience down further and essentially use separate pairs of microphones optimized to more ideally capture these different aspects, then combine them afterwards.  I feel this results in a better overall result than trying to find a good "middle of the road" optimization using a single pair of microphones.  The trick is that this must be done in such a way that the separate pairs support rather than fight each other, and the devil is most definitely in the details with respect to achieving that.  It's easy to make a mess of it and just complicate things without really improving the end result.  Still, I commonly argue for this somewhat unusual approach here at TS.  That's partly because I feel audience-perspective music recording is a unique recording endeavor compared to other forms of recording- For one thing, audience perspective recording is typically done from a considerable distance from the source.  It represents a very ambient recording situation regardless of whether we like that or not. In addition, we have far less control over the situation and the techniques I'm suggesting provide some additional control and flexibility;  And lastly because I find the presentation more convincing for both "modes of listening" - I can mentally switch back and forth and get a better feel for both than I can with straight 2-channel near-spaced microphone techniques. 

I see these things as possibly being applicable to your nature and ambience recordings as well.

Consider what you are recording and what you want to convey to the listener.  Then consider recording approaches which are optimized for what you want to convey.  If it's relaying a feeling being there in that place with a convincing immersive ambience, a spaced A/B technique with open pattern mics such as omnis is hard to beat.  If its a clear and precise focus on a particular sound within a particular soundscape, a single microphone or a coincident (X/Y, Mid/Side) technique using highly directional mics like the Schoeps MK41's can achieve that.  If you want both at the same time, you may be able to find a "middle ground" near-spaced approach which works for both aspects without compromising either too much. Or you can optimize separately for each aspect, and make a composite recording which better portrays both of them.  All depends on what you want to achieve, and how much effort you want to put into it.

For what you are doing the composite approach would probably mean setting up a spaced A/B omni recording to capture the ambience, and focusing a single MK41 directly on the subject of interest from a not overly distant location.  If the direct sound from subject of interest has stereo qualities to it which you'd like to convey in addition to the atmospheric stereo ambience from the A/B pair, you might consider using both MK41 in a narrow X/Y configuration (or better, a Mid/Side setup using one MK41 plus a figure-8 such as the MK8). Narrow so that neither mic of the pair is very far off-axis from a direct line to the source (which is why a Mid/Side setup works well for this - the Mid microphone is always pointed directly at your source), thus retaining good direct focus on the subject while still getting sufficient direct imaging type stereo-ness. And also narrow because the A/B omni pair will be contributing plenty of the other kind of stereo-ness, meaning less stereo-ness is required from the "direct sound" focused pair for a good overall listening impression.

« Last Edit: June 25, 2018, 06:45:14 PM by Gutbucket »
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Online Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 12236
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #11 on: June 25, 2018, 07:08:22 PM »
^ I don't know if that's "how it's typically done" in the nature, ambience, and effects recording world or not.  Some will certainly feel that what I'm describing is not how it's typically done for live music recording either, but I'd argue this is basically what a AUD+SBD mix recording is achieving. 

To me this is a "bottom up" approach, starting from basic fundamental room acoustic and human hearing aspects and building a recording approach based upon those things with a target recording situation in mind- in which case the question becomes, What is most important and how do I go about translating that. Rather than working "top down" and starting from an presumed stereo pair of microphones in order to produce a stereo recording- in which case the question is a much higher level one, essentially- How do I setup a pair of microphones to make a stereo recording in such and such a situation.

Apologies if this is all a bit too philosophical, but it's what keeps me excited about recording as a gateway to listening.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline morst

  • Archivist: Camper Van Beethoven & Cracker
  • Trade Count: (1)
  • Needs to get out more...
  • *****
  • Posts: 2633
  • Get in touch if you wanna record Cracker or CVB!
    • Soundscape Preservation Society
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #12 on: June 25, 2018, 07:13:58 PM »
This thread turned really interesting!

The Mid/Side control assumes the use of equal sensitivity mics and matched gain between channels.  In addition to the Mid/Side ratio you specify in whatever control you are using, any difference in sensitivity between the Mid and Side microphones and any difference in recording gains between the two channels also affect the Mid/Side ratio.  This is an additive "in addition to" thing (similar to the total gain being the sum of all gain stages- such as preamp gain plus recorder gain)
It must be hard to get perfect input levels with ganged-quads when attempting to work with Ambisonic formats.

Rather than working "top down" and starting from an presumed stereo pair of microphones in order to produce a stereo recording- in which case the question is a much higher level one, essentially- How do I setup a pair of microphones to make a stereo recording in such and such a situation.

Apologies if this is all a bit too philosophical, but it's what keeps me excited about recording as a gateway to listening.
When all you have is a pair of microphones, to mix a metaphor, everything looks like a nail!
Teams: Neumann, Bay Area Tapers, Multitrack, Pioneertown Tapers, Mac Geeks, Cassette Masters, Poster Collectors, Alumni of teams St Louis, Upper Midwest & Milwaukee / Southern Wisco

Online Gutbucket

  • record > listen > revise technique
  • Trade Count: (13)
  • Needs to get out more...
  • *****
  • Posts: 12236
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #13 on: June 26, 2018, 09:57:29 AM »
It must be hard to get perfect input levels with ganged-quads when attempting to work with Ambisonic formats.

Yes, that's why the ability to "gang" or link the input gain controls on recorders used with ambisonic microphones becomes important. Ambisonics is multichannel Mid/Side.  Because there are typically four or more channels involved in the matrixing (3 at a bare minimum) rather than just two, it's critical to have microphone sensitivities and recording channel gains matched closely across all channels for the matrixing to work properly.

Unlike 2-channel Mid/Side where if the Mid and Side sensitivities and gains are not matched one can simply dial it in by ear ignoring the ratio number displayed in the Mid/Side controller, with ambisonics one needs to be careful to keep the gain the same at all times across all channels - preferably control linked, as that makes adjustment of all channels together easy if necessary.  The work-around for recorders which do not allow one to calibrate levels and gang the gain controls together is to set reasonable gains at the start of recording, not change gain during recording, record a short segment of the same test tone to each channel using the same gain settings as used during the recording, determine the level difference between the recorded test tones on the computer, and apply the differences in makeup gain across all channels prior to matrixing.   Much easier to make sure all gains are equal beforehand and remain that way during the recording.
« Last Edit: June 28, 2018, 09:06:15 AM by Gutbucket »
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations> virtual teleportation time-machine experience
made easy- >>Improved PAS table<< | made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline heathen

  • Trade Count: (15)
  • Taperssection All-Star
  • ****
  • Posts: 1221
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #14 on: June 26, 2018, 10:54:50 AM »
It must be hard to get perfect input levels with ganged-quads when attempting to work with Ambisonic formats.

Gutbucket pretty much covered this, but I'll add that I just look at whichever channel is getting the highest levels and adjust my levels according to that.  Note that I've got all four channels linked with the F8, so I'm still adjusting the gain equally for each channel.  Since the four capsules are oriented in different directions, though, it makes sense that one will have higher levels than the others.
Mics: Core Sound TetraMic | AT4031s | AT AE5100s | AT853s (C/SC) | Line Audio CM3s | CA-14 omnis | Studio Projects CS5
Pre: CA9200
Decks: Zoom F8 | Roland R-05

Offline DSatz

  • Site Supporter
  • Trade Count: (27)
  • Needs to get out more...
  • *
  • Posts: 2502
  • Gender: Male
Re: Stereo Technique with MK41 or other super-cardioid Microphones
« Reply #15 on: June 27, 2018, 02:18:16 PM »
just want to point out that heathen's reply is correct; for Ambisonic decoding to work, the GAIN of each recording channel must be exactly the same. Normally no effort should be made to make the levels equal; it's the gains that count. In any real-world recording the peak levels will almost certainly differ among the four channels, and that is as it should be.
  • Gain is the degree of amplification that occurs between point A and point B in a circuit or system. It can be "unity" a/k/a 0 dB, or it can be some positive number of dB or it can be negative, in which case the minus sign is usually dropped and then the number that remains is the amount of loss.
  • To calibrate the gains of the four channels precisely, if you can record some rehearsal material, make a rough setting so that all four controls are as similar as you can get them "by eye" and the highest individual level obtained via the microphone doesn't quite reach 0 dB. Note which channel had the highest peak levels. Then don't touch that one channel's record level control; we're going to adjust the other three channels to match its gain. Disconnect the microphone, and connect a signal generator to that channel, set the generator to some midrange frequency, and adjust its output level (not the recorder's level) so that the meter on that channel reads exactly 1 dB below full scale (assuming that your meters have a nice, clear marking for that exact level; if not, choose the exact level with the clearest marking available). Then attach the generator to each of the other three channels in turn--or if you can split the signal, do that; either way, don't adjust the generator's level, but instead set the record levels in the other three channels all to exactly the same level as you set the first channel to.
  • If you don't have any rehearsal or "throwaway" material, just set the levels the best you can, but conservatively enough that you definitely won't need to change them during the recording. At the end of the recording, again without touching the recording levels, use a tone generator to record a midrange reference tone on each channel (or on all four at once if you can split it). The level can be anything that's convenient below 0 dB. Then when you go to decode the recording, adjust the decoder's input level controls to make those four recorded signals all have equal levels.
--best regards
« Last Edit: June 27, 2018, 02:35:14 PM by DSatz »
music > microphones > a recorder of some sort

 

RSS | Mobile
Page created in 0.313 seconds with 43 queries.
© 2002-2018 Taperssection.com
Powered by SMF